Voice operated switch for a duplex system



July 15, 1947. Q TSHUM| 2,424,069

VOICE OPERATED SWITCH FOR DUPLEX SYSTEMS Filed .July 16, 1945 Patented July l5, 1947 DUPLEX SYSTEM Otto Tschumi, Soleure, Switzerland, assignor t Autophon Aktiengesellschaft, Soleure, Switzerland, a joint-stock company of Switzerland Application July 16, 1945, Serial No. 605,402' y In Switzerland Getober V,21, 1944 VThis invention relates to an arrangement for changing over the direction of transmission in duplex systemsvior loud traffic.

Such arrangements are quite common and were hitherto effected by a switching device which, being in readiness for changing-over at the conclusion of audible signals, operated the change-Y over of the direction of transmission automatically at this stage (as for instance in the case of the switch device being controlled by a timedelay-relay). In these arrangements, it was further possible, independently of the conclusion ofthe audible signals, by means of manually operated equipment, to bring about a changeover of the direction of transmission.

The present invention relates to an arrangement for changing-over the direction of transmission in duplex systems for loud traiiic, in which the changing-over of the direction of transmission usually takes place at the conclusion of the conversation or at any convenient moment during the conversation, without the use of a manually operated equipment. The switching is done by simply speaking into the microphone at the station wishing to call the other.

According to the invention the arrangement for changing-over the direction of transmission in bridge-duplex systems for loud trafc is characterized in that the microphone and loudspeaker circuits are connected through a differential-relay, the drive-armature of which can take up two working positions and one normal position. The relay is oppositely energised by the microphone and loudspeaker circuits respectively, hence modifying the condition of the switching-device on which the direction of transmission depends.

The accompanying drawing illustrates, by way of example, an arrangement according to the invention.

Both stations STI and ST2 are connected over the line L. Each station is equipped with a microphone M, a loudspeaker La, amplier equipment, i. e., amplifiers for outgoing microphone and incoming loudspeaker voice-currents Am and Ala, and finally a bridge duplex switching apparatus in the line L at Br. In addition a balancing net system NW is symmetrically arranged with respect to L at B1'. The switches rc2 and TCS, controlled by a relay RC of an accessory switching apparatus at the station, opens the out-going circuit o f the amplifier Am associated with the microphone and closes the incoming circuit of the amplifier associated with the loudspeaker, respectively.

A differential relay ML having windings M z claims. (c1. 179-1) and L, loops out-going circuits of the ampliiiers'- via the rectiiiers RI and'RZ. The two windings ofA the differential relay control the contacts l and m of the accessory switching apparatus, the latter consisting of the afore-mentioned relay RC, a relay TR, and twofswitches a and tr. The switching arrangements of the two symmetrical stations illustrated in the diagram cor-A responds to a changing-over interval in the conversation during which STI takes over the transmission and ST2, the receiving'. This switching arrangement in operation position is normal after origination of a call. y

On speaking into the microphone M at Stl the voice-current ows through the loudspeaker La -at ST2 via the amplier Am at STI, the switch rc2,'both bridge duplex switches Br, the amplier Ala at ST2 and the switch-TCG. -In this yway the winding M at STI and the winding L at ST2 are energised.v Consequently the contact m closes and operates the relay TR. The closing of the relayv contact t1' has no further electrical effect onthe non-energised relay-RC on account of the latter being-short circuite'dby the switchm. Y

At srz the switch Zenom-circuits the remy' ing energised as before.` l y. The switches rc2v and rc6 on which the di- TR, the contact ltr-releases, the relay RC remainrection'of transmissionv depends are controlled-by'v relay RC. The electrical condition of relay RC remaining unaltered, no change in the direction of transmission occurs. Such a change can be operated only when the voice-current ceases, hence causing the switching apparatus to come automatically into action. In this case the, electric state of STI is as follows:

The winding M of the differential relay ML is energized opening the contact at m, which, up to the present, short-circuited relay RC, so that this relay, already energised by a current flowing across switch tr, controls in its turn the closing and opening of contacts rc2 and rcl respectively, thus bringing about a change-over in the direction or transmission.

The opposite switching condition is effected at ST2 in that the winding L is energised opening contact l, which, in further consequence of tr being open, releases the relay RC. As a result, the switching-over of contacts rc2 and TCG is brought about and ST2 takes over the transmission (calling) STI the receiving.

On speaking now into M at ST2, the Voicecurrent flows through La at STI and the electric condition will be respectively exactly the same as abovedescribed.

Now take for instance the case of the callingstation being at STI and of ST2 wanting to interrupt the conversation, i. e., Wanting to change 5 the direct-iontpftransmission. All heahasla-to do.- is to speaksintoM at ST2.4 The following changes: take place:

On energising the Winding M of the diierential. relay IM at ST2, the magnetic field set up in Lv l0 can be practically counterbalanced@and theecon-V tact Z will open. Under the former condition; the` relay TR was short-circuitedbytheclosedcontact.

l, released the contact tr so: that no;Y current;

owed through RC, thus prepari-ngethe'fstation foriA 15v calling. The respectively samechanges take place.

at STI, for, on energizing Winding L,..of"the;.df'=j` ferential relay ML, the magnetic field induced by M will be counterbalanced, contact'. m'cwi'll open, relay RC will be energised and consequently 20 thecchange-overof the-direction of transmission.- is-efected,at STI. Upon hearing-:the'audible`r` signale from ther loudspeaker at STI givenA by the-:operator attSTZ, the :operator at; STI will ceaseff-to `callyinto hismicrophone. By,Ak consequence, the windingM at ST2. andI L at STI will be energisedl causing ,thei-r, correspondingcontacts to close,4 whereby therelays Rcfwill beelectrically.- im-munebut'will.beprepared fora new changeover.. in the. directionfof:.transmission at some 30 convenient interval.-

Independent :of fthe electric state-of :theswitching arrangement according tovw the. invention, whether STI or :ST2: is playing the part f of the calling.; orreceivingf'statiomr not,A itis. only, 35 necessary `forthe operatorfwantingto Acall to speak.v into his microphonef.in..order. to. -bringaabout a changefover Y in4 the, ,direction of transmission.

The :arrangement according j to. the invention cancfgcoursebe combined :with any of the,accesf 40 soryf` switching', apparatusA in use .in telephony.` Intthis, way-a--time-,delay-relay can loe-introduced, to. fguard, ,from being, subjected .to changing-over. Within certaintime limitsf the changefoverbe ing eiected after intervals of more orlessfcone- 45 siderablerlength,

A. certain amount of, acoustic; interference1 (echo) at each end is inevitablerin sensitiveeapfparatusmut Vit .can be V,reducedto a minimum by constructing., the microphoneemouthpiecefade-. 50

4. quately. In some arrangements in which the electro-acoustic-transformer serves the two purposes of sending and receiving voice-currents, electric interference can result.

The balancing of the bridge impedance, depcndingfgonstheerange of fthe line ,overwhich the stationsrare zlooped, is efiectedponrthe bridge itself within very narrow limits. The incoming voice-current could also be converted with respect to frequency, and a corresponding frequency range:limiting device could take the place of the impedance bridge, hence practically avoiding any back-,feed Within .the station equipment. The voiceecurrent frequency can without harm be reconvertedon` its passage over the amplifier Ala.

What I.claim is;

1. .Inca duplexsystem for loud traflic, a loudspeaker circuit, a microphone circuit, control contacts'in said circuits for connecting and disconnecting the loudspeaker and the microphone, adiierential relayv .connected inbetween :said-circuits..a relayfior:operatinggsaid contacts, an iaddi tional circuit including the contactoperatingzre.- lay, andcontrolcontact-sin the additional circuit 5 operated' Tbyfsaid 'differential relay.

2. In..a: duplexsystern for loudA tralc, `a loud-- speaker-circuit, azmicrophone circuit, control coni tacts .in'said .circuits-:for connecting: anddiscon.

necting,r `the -f loudspeaker and. the microphone, an differential relay` connected invbetween. said :.cir.:- cuits, an additional circuit including two branches connected.Y in Vparallelpa-` Contact and a. relay in'- eachoifithetbranches, Lonefoi the branch relays: operating Athescontrol contacts, the branchxcon: tacts being operable| by the diierentialrelay; and

a contact between the branches. operable` byf the other branchrelay;` toy short .circuit v one-i of 11 the branch* relays.accordingto the position ofi the.:

branch contacts.

OTTO TSCHUML..

REFERENCES f CITED Tiieiollowing references are oi ile of this :patent:

UNITED. STATES. PATENTS recordv infl the 

